Thermal current responsive circuit breaker



Aug 31, 1965` w. H. NASH ETAL 3,204,063

THERMAL CURRENT RESPONSIVE CIRCUIT BREAKER Filed Sept. 19, 1962 4Sheets-Sheet l 7f3 7 /zz 22d/4M 2224/4470 lesa/440 Z a3 Il" IZ, f I;

I ray mvENToRs. m4/.MM H. NASH EEZ/5WD Z//. K/Q/V//VSKY n m f, jai/w( MM@rfa/@Nay Aug. 31, 1965 w. H. NASH ETAL 3,204,063

THERMAL CURRENT RESPONSIVE CIRCUIT BREAKER Filed Sept. 19, 1962 4Sheets-Sheet 2 INVENTORS. Zl//LL//V/ H. NAF/'f Aug. 31, 1965 w. H. NASHETAL 3,204,063

THERMAL CURRENT RESPONSIVE CIRCUIT BREAKER 4 Sheets-Sheet 3 Filed Sept.19, 1962 Aug. 31, 1965 W. H. NASH ETAL THERMAL CURRENT RESPONSIVECIRCUIT BREAKER Filed Sept. 19, 1962 4 Sheets-Sheet 4 f/Z INVENTORS, Y@w/L/Aw H, N45# LM LUM United States Patent() 3,204,063 THERMAL CURRENTRESPONSIVE CIRCUIT BREAKER William H. Nash and Edward W. Kaminsky, SouthMilwaukee, Wis., assignors to McGraw-Edison Company,

Milwaukee, Wis., a corporation of Delaware Filed Sept. 19, 1962, Ser.No. 224,636 8 Claims. (Cl. 200-116) This invention relates to circuitbreakers and more particularly to circuit breakers which have particularbut not exclusive application to the protection of electrical apparatussuch as traansformers.

Distribution class transformers are often provided with circuit breakerswhich open the secondary circuit upon thev occurrence of a short circuitacross the secondary leads or when prolonged overloads heat thetransformer to a point Where the secondary circuit must be opened toprevent insulation damage. For this purpose circuit breakers areprovided with thermal and overcurrent responsive elements adapted toopen the circuit breaker contacts upon the occurrence of such overloads.In addition, such devices may also include a signal light assembly forgiving an external indication that the device being protected has beensubjected to an overload.

It is an object of the invention to provide a new and improved threepole circuit breaker for use -in three phase transformers and which areresponsive both to the temperature of the transformer dielectric fluidand to overload currents in the secondary leads.

Another object of the invention is to provide a three pole circuitbreaker having a single operating mechanism and which is operative tointerrupt current simultaneously in each phase upon the occurrence of anoverload in any one of the phases.

These and other objects and advantages of the instant invention willbecome apparent from the detailed description thereof taken in view ofthe accompanying drawings in which:

FIG. l is a front elevational view of the circuit breaker according tothe instant invention;

FIG. 2 is an exploded perspective View of the operating mechanism of thecircuit breaker shown in FIG. l;

FIG. 3 is a view taken along lines 3-3 of FIG. l except that the circuitbreaker contacts are shown in open position;

FIG. 4 shows the circuit breaker operating mechanism in an unlatchedposition with the main contacts open;

FIG. 5 shows the circuit breaker operating mechanism when it is latchedand the main contacts are open;

FIG. 6 shows the circuit breaker operating mechanism when it is latchedand the main contacts are closed and is taken along lines 6-6 of FIG. 1;

FIG. 7 is a View taken along lines 7-7 of FIG. l; and

FIG. 8 is a View taken along lines 8 8 of FIG. 7.

Referring now specifically to FIGS. 1 and 2, the invention is shown tocomprise a three pole automatic trip free circuit breaker 9 mounted on asuitable base 10. Each pole is identical .and includes a contactassembly 12 and an over-current responsive assembly 14. A commonoperating and latch assembly 16 holds each of the contact assemblies 12in closed position and is operable to simultaneously release 'all ofsaid Contact assemblies upon the actuati-on of any one of theovercurrent assemblies 14. Prior to the release of the operatingmechanism 16 and the consequent opening of the contact assemblies 12,each of the overcurrent responsive ice assemblies 14 is operable toactuate a signal light mechanism 18 so that an external signal is givento -indicate that the system or device being protected has beensubjected to 'an overload.

The base 10 includes a base plate 11 and a pair of panels 19 and 19aextending normally from the plate 11 to support the operating mechanism16 and the signal light mechanism 18 adjacent one side of said assemblyas seen in FIG. l. A third support panel 20 is aixed to the base 10 anddisposed adjacent the opposite side and is interconnected with thepanels 19 by crosspins 21. The base plate 11, panels 19, 19a and 20 andthe crosspins 21 provide a relatively rigid supporting structure for thecontact assemblies 12, the overcurrent assemblies 14, and the operatingmechanism 16.

A plurality of insulating panels 22 separate the poles 11 from eachother and from the support panels 19 and 20. As seen in FIGS. 1 and 3,the insulating panels 22 are substantially co-extensive with the supportpanels 19 and 20 and are rigidly secured thereto by the crosspins 21. Asseen in FIGS. 2 and 3v each phase is also provided with a rst insulatingmember 23 for supporting its contact assembly 12 and a second insulatingmember 24 for supporting its overcurrent assembly 14. Crosspins 25extending through the side panel 20 in each of the insulating panels 22,rigidly afx the insulating members 23 to the base 10 while theinsulating members 24 are ailixed thereto by one of the crosspins 21 anda second crosspin 26 extending through the panels 20 and 22.

Each of the contact assemblies 12 is shown in FIGS. 2 and 3 to include amovable contact member 27 and a cooperating fixed contact 28 which ismounted on the insulating member 23. The movable Contact 27 is carriedat one end of a contact carrier arm 29 which is pivotally connected atits other end by means of a pin 30 extending through the legs of aUeshaped bracket member 31 aflixed to the upper end of the insulatingmember 23.

The overcurrent responsive assemblies 14 each includes a bimetallicelement 32 which is affixed at one end to the insulating member 24 andwhich has an insulating bar 34 longitudinally afxed to its oppoiste endsby means of a rivet 35. An adjustable trip pin 40 is threadably receivedin the free end of each of the trip members 34 and each engages theupper surface of one of the trip fingers 41 associated with each poleand each of which is carried by a common trip bar 42 pivotally mountedby pins 43 on the support panel 20 and on the right-hand most insulatingpanel 22 as viewed in FIG. 1. A pair of insulating skirts 44 aredisposed on each of the insulating trip members 34 between the trip pin40 and the rivet 35 so as to increase the leakage path between thecurrent carrying bimetallic element 32 and the metallic trip pin 40 andtrip bar 42.

Referring now in particular to FIGS. 2, 4, 5 and 6, the operating andlatch assembly 16 is shown to include a generally U-shaped operatingmember 50 having a transverse operating rod 51 extending between itslegs 52 and 53 and through guide slots 51a in the panels 19 and 19a.Legs 52 and 53 are pivotally mounted at their ends at 54 on the supportpanels 19, 19a.

A latching mechanism 55 is disposed between the support panels 19, 19aand includes a latch arm 57 which carries a latch tip 58 at one end andwhich is pivoted at its other end on a lixed axis by means of atransverse pin 60 extending between the support panels 19, 19a.

An operating shaft 45 is pivotally mounted at its opposite ends betweenthe support panels 19a and 2G and has three U-shaped crank members 46affixed thereto. Each of the crank members 46 is adjacent one of thepoles and the free ends thereof are each pinned to an insulating link 47at 48. The other end of each insulating link 47 is pivotally connectedto its contact arm 29 at 49 so that clockwise rotation of operatingshaft 45 as viewed in FIG. 3, will simultaneously rotate each of thecontact arms 29 counterclockwise and thereby force the movable contacts27 into engagement with the fixed contacts 28.

The latch arm 57 is coupled at a point intermediate its ends to theoperating shaft 4S by an overcenter assembly 61 having a rst toggle link62 which is pivotally connected at 63 to the mid point of latch arm 57and a second toggle link 65 pivotally connected at 66 between the armsof a U-shaped crank element 67 affixed to the operating shaft 45. Theother ends of the toggle links 62 and 65 are pivotally connectedtogether by a knee pin 68. The overcenter assembly also includes a pairof parallel overcenter springs 70 which are connected at one end to theknee pin 68 and at their other ends to the transverse operating rod 51.

The latching mechanism S also includes a latch shaft 72 pivotallymounted between the support panels 19, 19a and having a half moon latchrecess 74 intermediate its ends. A reset arm 75 is aiixed to the shaft72 and both are urged toward counterclockwise rotation by a seer spring76 which engages the arm 75 at one end and is anchored to the supportpanel 19 at its other. A pin 78 extends transversely from the free endof the resetting arm 75 and engages the upper edge of a latch member 80which is pivotally mounted at 81 on an adjusting lever 83 which, inturn, is pivotally mounted intermediate its ends by a pin 84 extendingbetween the support panels 19, 19a. i

The latch member 80 has a generally inverted U-shaped configuration withone leg 86 depending from its pivoted end and comprising a latch fingerfor engaging the upwardly extending latch lip 87 of a latch plate 88which is affixed to a pivot pin 89 extending between the support panels19, 19a. A reset pin 91 extends transversely from the other leg of thelatch member 80 for cooperative engagement with a reset linger 92integral with the operating member 50 and extending generally upwardlytherefrom.

As seen in FIGS. l and 2, a crank 94 integral with the pivot pin 89,extends through support panel 19 and is disposed adjacent a trip pin 95extending laterally from the trip bar 42.

Operation of the latching mechanism will now be discussed in relation toFIGS. 2, 4, 5, and 6. As shown in FIG. 2, the operating member 5t) isadapted to be rotated by pivotal movement of an operating handle (notshown) disposed on the exterior of the apparatus being protected. Aconnecting rod 97 and a link 98, which threadably receives one end ofthe rod 97, connect the external operating handle (not shown) to theoperating member 50. Pivotal movement of the operating member 50, inorder to latch the mechanism 55 and to close and to reopen the contactassemblies 12, is accomplished by moving the operating rod 97 in agenerally upward and downward direction as viewed in FIG. 2.

Referring now to FIG. 4 which shows the operating mechanism 16 in itsunlatched position with the contact assemblies 12 open, it can be seenthat the transverse rod 51 engages the lower edge of the latch arm 57.In order to operate the mechanism 16 to the latched position shown inFIG. 5, operating member 5l) is pivoted clockwise whereby transverse pin51 forces counterclockwise rotation of the latch arm 57. In addition,counterclockwise pivotal movement of operating member 50 will bring theintegral reset inger 92 into engagement with the transverse pin 91 onthe latch member 80 thereby rotating the latter clockwise about pin 81,and against the action of a spring 100 which is anchored to the panelmember 19.

As operating member 50 continues to rotate counterthemselves.

clockwise, the clockwise rotation of latch 99 will continue as the pin91 rides on the curved surface 181 of the reset nger 92 until the latchfinger 86 on member 80 moves past the latch lip 87 of the latch plate88. After the latch finger 80 has moved free of the latch lip 87, asshown in FIG. 5, a spring 102, extending between an eyelet 184 in theupper surface of the latch plate 88 and the panel member 19, rotates thelatch plate 88 through a slight clockwise angle until the lip 87 isdisposed in the path of the latch finger 86 whereupon further rotationof latch plate 88 is prevented by the engagement of the trip pin 95 bythe crank 94, see FIG. 2.

As stated hereinabove, counterclockwise rotation of operating member 50also pivots the latch finger 57 connterclockwise to move its latch tip58 toward the half moon latch 74. Simultaneous with this action, therotation of the latch member 80 by the reset finger 92 allowscounterclockwise rotation of the shaft 72 by the seer spring 76 as thepin 7 8 on the arm 75 follows the movement of member 80. The half moonlatch 74 is therefore in its position shown in FIG. S as the latch tip58 approaches. Engagement of the latch tip 58 with the fiat portion ofthe half moon latch 74, will rotate the shaft 72 through a slightclockwise angle until the latch tip 58 has moved past, whereupon shaft72 will return to its position shown in FIG. 5 by the -spring 76 tolatch the arm 57 in its position shown in FIG. 5.

It can be seen that as the latch arm 57 was moved from its positionshown in FIG. 4 to its position shown in FIG. 5, the toggle link 62moves the knee pin upward and to the left as viewed in FIG. 4 until itassumed the position shown in FIG. 5. Because the position of the kneepin 68 in FIG. 5 is not at the center of curvature of the guide slots51a, the end of the overcenter spring 70 attached to pin 51 will berotated through an arc whose radius is longer than the relaxed length ofthe springs As a result the springs 7th Will be extended so that energywill be available to rapidly close the contacts 12 and to separate themrapidly upon tripping.

When the operating mechanism 16 is in its latched position shown in FIG.5, the Contact assemblies 12 may be closed by rotating the operatingmember 5t) clockwise to its position shown in FIG. 6. As the operatingmember 50 pivots, the ends of the overcenter springs 70 that engage thetransverse pin 51 are moved downwardly as Viewed in FIG. 5 while theother ends thereof momentarily rernain stationary. When the line ofaction of the springs 70 passes the pivot point 63 of toggle link 62 asthe operating member 50 moves clockwise, the toggle assembly will becomeovercentered causing knee pin 68 to snap from its position shown in FIG.5 to its position shown in FIG. 6. This brings the link into toggle withthe link 62 to snap the crank 67 and the operating shaft 4S clockwise.It can be seen with reference to FIG. 3 that clockwise rotation of thecrank shaft 45 will move the contact arms 29 counterclockwise and themovable contacts 27 into engagement with stationary contacts 28. It willbe appreciated also that because of the downward movement of the kneepin 68 during the closing of the contact assembly 12, the overcentersprings are somewhat shortened so that a portion of their .stored energyis utilized in the closing of the contact assembly 12.

The operating sequence during manual opening of the main contacts issubstantially opposite to that of the closmg operation just explained.Here the operating member 50 is rotated counterclockwise from itsposition shown in FIG. 6 to its position shown in FIG. 5. When the lineof action of the overcenter springs 70 pass the pivot point 63, thetoggle will be broken and pin 68 will snap upwardly from its positionshown in FIG. 6 to its position shown in FIG. 5. This rotates theoperating shaft. 45 counterclockwise to open the Contact assemblies 12..Latch arm 57 and latch member 80 will, however, remainl latched as shownin FIG. 5.

Referring now specifically to FIGS. 2 and 3,.,t`he elec trical currentpath through each pole of the device when the contact assemblies 12 areclosed, is from a first conductive terminal member 106 affixed to theinsulating member 23 and electrically connected to the stationarycontact 28; through the lixed and movable contacts 28 and 27respectively; through a iiexible conductive member 107 attached at oneend to the movable contact 27 and at its other end to a rigid conductivemember 109 which is held in electrical engagement with the bimetallicelement 32 by the rivet 35; through the bimetallic element 32; and out asecond terminal 110 in electrical engagement with the bimetallic element32 and mounted on insulating member 24. If the device is used to protectan oil-immersed transformer, the base is normally mounted below the oillevel by means of bracket members (not shown). As a result, thebimetallic element 32 in each pole is subjected to heating as a resultof the flow of load current therethrough and due to the temperature ofthe ambient oil. Should the 12R lost due to a high magnitude overcurrentheat any of the bimetallic elements or should the elements be heated bya low magnitude overcurrent in the transformer windings which heats thesurrounding oil, or should a combination of both cause downwarddeflection of the left end of any of the bimetallic elements 32, asviewed in FIGS. 2 and 3, the consequent downward movement of the trippin 40 will rotate the trip bar 42 clockwise. As a result, the trip pin95 will move downwardly to rotate the latch plate 88 counterclockwisethrough the agency of the crank 94. If such rotation of latch plate 88be sufficient to move the latch lip 87 out of latching engagement withthe latch finger 86, latch member 80 will be free to rotatecounterclockwise under the influence of spring 100 from its positionshown in FIG. 6 to its position shown in FIG. 4. As a result of theengagement between the upper edge of latch member 80 and the transversepin 78 on the arm 75, the latch shaft 72 and the half moon latch 74 willrotate clockwise as the spring 100 overcomes the seer spring 76. Thelatter action releases the latch arm 57 for rapid clockwise movement asthe overcenter springs 70 contract. This moves the knee pin 68 from itsposition shown in FIG. 6 to its position shown in FIG. 4 to therebybreak the toggle linkage 62, 65. The operating shaft 45 is therebyrotated counterclockwise to simultaneously open the contact assemblies12 and interrupt the circuit through each. The energy of the latch arm57 impacting the transverse rod 51 is taken by a shock absorbing spring112 mounted below rod 51 and aixed to the frame 10.

The amount of downward deflection of the bimetallic elements 32 andhence, the magnitude of the overcurrent necessary to trip the device maybe adjusted by varying the amount of overlap between the latch iinger 86and the latch lip 87 through the agency of the adjusting link 83 or theadjustable trip pins 40. Rotation of the trip pins 40 allows the amountof deflection required of each bimetallic element 32 to trip the deviceto be individually adjusted. For simultaneous adjustment of all thephases an adjusting screw 113 extending through panel member. 19 andengaging the link 83 produces rotation of said link about pivot 84 so asto move the latch linger 86 upwardly and downwardly relative to thelatch lip 87.

The signal light assembly 18, shown in FIGS. 1, 2 and 7, is provided togive an external indication that the device being protected has beenoverloaded and includes a movable Contact latch member 115, and astationary contact member 116 and is normally adapted to be tripped uponthe occurrence of an overload current less than that necessary to causetripping of the circuit breaker itself. Suitable insulation 117electrically insulates the stationary contact member 116 from themetallic panel member 19a. Movable contact latch member 115 is rotablymounted at 118 on an L-shaped adjusting bar 120 and includes a latch tip121 adapted to engage the latch lip 87 of the latch plate 88. Adjustingbar 120 is slidably mounted on the panel 19a by means of a slot 126formed in said panel and which receives the pivot pin 118. Upward anddownward movement of the pivot pin 118, in order to vary the overlapbetween latch tip 121 and latch lip 87, is accomplished by means of anadjusting screw 122 which engages the adjusting bar and the panel 19a.

When any of the bimetallic elements 432 are heated to the point wherelatch plate 88 is sutiiciently rotated to release the latch tip 121, thecontact member 115 will be rotated clockwise as viewed in FIG. 7, underthe influence of a seer spring 123, until a contact ear 124 engages thestationary contact 116 thereby grounding stationary contact 116 to theframe to complete the circuit through a current transformer 125,inductively coupled to one of the leads of the protected device, and asignal light 127, whereby the latter is energized.

The signal light assembly 18 is also provided with a resetting crank 128pivotally mounted at 129 on panel 19a. A leaf spring 130 is affixed tothe lower end of the reset crank 128 and its free end is disposed belowthe transverse rod 51. It can be seen in FIG. 7 that counterclockwiserotation of operating member 50 will rotate the reset crank 128counterclockwise from its full position to its phantom positionwhereupon a transverse pin 132 will engage a reset ear on the movablecontact latch member 115 to rotate the latter counterclockwise to itsphantom position whereupon latch tip 121 will re-engage the latch lip87.

The signal light assembly will normally be set to trip upon theoccurrence of a smaller overload current and that necessary to trip thecircuit breaker itself. This is accomplished by providing a .smalleroverlap between the latch tip 121 and the latch lip 87, then between thelatch finger 86 and said latch lip. In operation, therefore, apredetermined overload current in one of the poles will rotate the latchbar 88 sufficiently to trip the signal light assembly, therebyenergizing the signal light 127 while the main contacts remain closed.Should the overload current thereafter increase a suflicient amount, themain contacts will then be tripped open.

Because the signal light assembly 18 is tripped by an overload currentwhich is insufficient to trip the circuit breaker itself, assembly 18should be reset without tripping the circuit breakers main contacts.This is accomplished by counterclockwise rotation of operating member 50is viewed in FIG. 7 in a manner described above. It can be seen that inthe resetting of the signal light assembly 18 operating member 50 ismoved in the opposite direction from that during the manual trippingoperation, previously described, so that resetting of the signal lightassembly cannot cause accidental tripping of the device. In the eventthat the signal light assembly has been tripped by an overload currentwhich is also suiiicient to trip the circuit breaker itself, the signallight assembly will be reset when the main contact assemblies 12 areclosed by the action of the operating member 50 in moving the latchingmechanism 55 from the position shown in FIG. 5 to its `position shown inFIG. 6.

The signal light resetting crank 128 performs the additional function oftesting the signal light without tripping the latch tip 121 or the maincontacts 12. In order t0 determine whether the signal light 127 isoperable, the operating member 50 is rotated counterclockwise in FIG. 7to rotate the reset crank 128 counterclockwise until the pin 132 engagesthe reset arm 133. Further, rotation of the operating member 50 willcause rotation of the contact member 115 in opposition to the spring 123until a second contact iinger 135 is moved into engagement with thestationary contact 116 to co-mplete the circuit through the signal light127, and if operating it will light. It will be appreciated that thelatter operation is accomplished without tripping the signal light latch121 and without moving the operating member 50 in a direction whichwould result in opening of the main contacts 32.

While only a single embodiment of the invention is shown and described,it is intended to cover in the 7 appended claims all modifications whichfall within the true scope and spirit thereof.

We claim:

1. A three pole circuit breaker including a base, each pole including abimetallic element and fixed and movable contact means, a singlelatching assembly common to all of said poles, said latching assemblyincluding first and second independent pivotal latching members andfirst and second independent pivotal holding members for respectivelymaintaining said first and second latching members in a latch position,spring means resiliently urging said second latching member intoengagement with said first holding member for resiliently urging saidfirst holdingl member toward pivotal movement in a latch releasingdirection when said second latch member is released from its latchedposition and allowing said first holding member to return to its holdingposition when said second latch member is in its latched position, anovercenter assembly coupled to said first latching member and to each ofsaid movable contacts for simultaneously moving said contacts betweenopen and closed positions, an operating member movable from a firstposition to a second position to latch each of said latching members onits associated holding member, movement of said operating member fromits second position to said first position placing said overcenter meansin a rigid condition to close said movable contacts, a common trip barcoupled to said second holding member and rotatably mounted on saidbase, said trip bar having a trip finger adjacent each of saidbimetallic elements so that the deflection of any of said elements as aresult of an overiload current through its pole will rotate said tripbar and said second holding member to release said second latchingmember for rotation by said spring means to pivot said first holdingmember out of latching engagement with said iirst latching member and torelease said overcenter means for the simultaneous opening of each of.said movable contacts.

2. A three pole circuit breaker including, a base, each pole including abimetallic element fiXedly mounted adjacent one end on said base and afixed and movable contact, a single latching assembly common to all ofsaid poles, said latching assembly including first and secondindependent pivotal latch members and first and second independentpivotal holding members for respectively maintaining said first andsecond latch members in a latched position, said first holding memberand said second latch member being elongate and pivotally mountedadjacent one end, first spring means resiliently urging said secondlatch member away from its holding element, second spring meansresiliently urging the other end of said first holding member intoengagement with the other end of said second latch member the springforce of said first spring means being substantially larger than that ofsaid second spring means so that said first holding member is pivoted ina latch releasing direction When said second latch member is out of itslatched position and allowed to return to its latching position whensaid second latch member is in its latched position, an overcenterassembly coupled to said first latch member and to each of said movablecontacts, an operating member movable in a first direction to engageeach of said latch members for movement toward their associated holdingmembers, movement of said operating member in a second direction aftersaid latch members are in a latched position placing said overcenterassembly in a rigid condition to simultaneously close each of saidmovable contacts, a common trip bar engageable with said second holdingmember and rotatably mounted on said base, said trip bar having a tripmeans adjacent each of said bimetallic elements so that the defiectionof any of said elements as a result of an overload current through itspole will rotate said trip bar and said second holding member to releasesaid second latch member and pivot said first holding member out oflatching engagement with said first latch member and to release saidovercenter means for the simultaneous opening of each of said movablecontacts.

3. A three pole circiut breaker including, a base, each pole including abimetallic element fixedly mounted adjacent one end of said base and afixed and movable contact, each of said movable contacts being mountedon a contact carrier pivotally mounted on said base, a single latchingassembly common to all of said poles, said latching assembly includingfirst and second independent pivotal latching members and first andsecond independent pivotal holding members for maintaining said firstand second latching members in a latched position, said first holdingmember and said second latching member being elongate and pivotallymounted adjacent one end, the other end of said second latching memberengaging the other end of said first holding member, spring meansresiliently urging said second latching member toward pivotal movementagainst said first holding member to pivot the latter in a latchreleasing direction when said second latching member is out of itslatched position, said first holding member being biased for return toits holding position when said second latching member is in its latchedposition, an operating shaft rotatably mounted on said base and coupledVto said contact carriers for simultaneously moving said movablecontacts between open and closed positions, an overcenter assemblycoupled to said first latching member and to said operating shaft, anoperating member movable from a first position to a second position tolatch Ieach of said latching members on its associated holding members,movement of said operating member from its second position to said firstposition placing said overcenter means in a rigid condition torotatesaid operating shaft into a switch closed position, a common trip barcoupled to said second holding member and rotatably mounted on saidbase, said trip bar having a trip means adjacent each of said bimetallicelements so that the deiiection of any of said elements as a result ofan overload current through its pole will rotate said trip bar and saidsecond holding member to release said second latching member and pivotsaid first holding member out of latching engagement with said firstlatching member and to release said overcenter means for thesimultaneous opening of each of said movable contacts.

4. A three pole circuit breaker comprising, a base, each pole includinga bimetallic element and a main fixed and a main movable Contact, acollapsible linkage assembly for opening said main movable contacts, alatching assembly for holding said main movable contact closed, anoperating member movable in a first direction to place latching assemblyin a latched condition, subsequent movement of said operating member inan opposite direction placing said linkage assembly in a rigid conditionto close said main movable contacts, trip bar means coupled to saidlatching assembly and rotatably mounted on said base, said trip meansbeing engageable by each of said bimetallic elements so that thedeflection of any of said elements as a result of an overload currentthrough its pole will rotate said trip bar means to trip said latchingassembly and release said linkage assembly for the simultaneous openingof each of said main movable contacts, a signal light assembly includinga signal light and a first contact member rotatably mounted on saidframe and a second contact member iixedly mounted on frame, said firstcontact member having a latch portion and a pair of contact portionsengageable with said second contact member upon rotation in eitherdirection, spring means resiliently urging one of said contact portionsinto engagement with said stationary contact, said latch portion beingengageable with said latching assembly to normally prevent rotation ofsaid first contact member, deflection of any one of said bimetallicelements unlatcliing said first contact member for rotation of one ofsaid contact portions into engagement with said second contact member tocomplete an energizing circuit through said signal light, relatchingmeans engageable by said operating member upon movement of the later insaid opposite direction after said movable contact has been closed beingoperative to relatch said first contact member, movement of saidoperating member in said opposite direction after said first contactmember has been latched being operative to move said other contactportion into engagement with said second contact member to test saidsignal light without tripping said main movable contacts.

5. A three pole circuit breaker comprising, a base, each pole includinga bimetallic element and a main fixed and a main movable contact, asingle latching assembly common to all of said poles, said latchingassembly including a pivotal latch member and a pivotal holding memberfor maintaining said latch member in a latched position, an overcenterassembly coupled to said latch member and to each of said main movablecontacts for simultaneously moving said contacts between open and closedpositions, an operating member movable in a first direction to move saidlatch member into latching engagement with said holding member,subsequent movement of said operating member in an opposite directionplacing said overcenter means in a rigid condition to close said mainmovable contacts, a common trip bar coupled to said holding member androtatably mounted on said base, said trip bar having a trip portionadjacent each of said bimetallic elements so that the deflection of anyof said elements as a result of an overload current through its polewill rotate said trip bar to trip said latching assembly and releasesaid overcenter means for the simultaneous opening of each of saidmovable contacts, a signal light assembly including a signal light and afirst contact member rotatably mounted on said frame and a secondcontact member fixedly mounted on said frame, said first contact memberhaving a pair of circumferentially spaced apart contact fingersstraddling said second contact member and a latch finger, spring meansresiliently urging one of said Contact fingers toward rotation intoengagement with said stationary contact, said latch finger engageablewith said holding member to normally prevent engagement of said onecontact finger and said stationary contact, deflection of any one ofsaid bimetallic elements unlatching said first contact member tocomplete an energizing circuit through said signal light, relatchingmeans engageable by said operating member upon movement of the latter insaid opposite direction after said movable contact has been closed beingoperative to relatch said first contact member, movement of saidoperating member in said opposite direction after said first contactmember has been latched being operative to move said second contactfinger into engagement with said second contact member to test saidsignal light without tripping `said main movable contacts.

6. A three-pole circuit breaker, each pole including overcurrentresponsive means and fixed and movable contact means, a single latchingassembly common to all of said poles, said latching assembly includingfirst and second independent pivotal latching members, first and secondindependent pivotal holding members for respectively maintaining saidfirst and second latching members in a latched position, biasing meansresiliently urging said second latching member into resilient engagementwith said first holding member for resiliently urging said first holdingmember toward pivotal movement in a latch releasing direction when saidsecond latch member is released from its latched position and allowingsaid first holding member to return to its holding position when saidsecond latching member is in its latched position, an overcenterassembly coupled to said first latching member and to each of saidmovable contacts for simultaneously moving said contacts between openand closed positions, an operating member movable from a first positionto a second position to latch each of said latching members on itsassociated holding member, movement of said operating member from saidsecond position to its first position placing said overcenter means in arigid condition to close said movable contacts, common trip meanscoupled to said second holding member and to each of said overcurrentresponsive means so that the occurrence of an overload current throughany of said poles will pivot said second holding member to release saidsecond latching member for rotation by said biasing means to rotate saidfirst holding member out of latching engagement with said first latchingmember whereby said overcenter means is released for simultaneousopening of said movable contacts.

7. A three-pole circuit break-er, each pole including overcurrentresponsive means and fixed and movable contact means, a single latchingassembly common to all of said pol-es, said latching assembly includingfirst and second independent pivotal latching members, first and secondindependent pivotal holding members for respectively maintaining saidfirst and second latching members in a latched position, said firstholding member and said first latching mem-ber being elongate andpivotally mounted adjacent one end, 'biasing means resiliently urgingthe other end of said second latching member .into resilient engagementwith the other end of said first 'holding member for resiliently urgingsaid first holding member toward pivotal movement in a latch releasingdirection when Isaid second latch member is rel-eased from its latchedposition and allowing said first holding member to return to its holdingposition when said second latching member is in its latched position, acollapsible overcenter assembly coupled to said first latching memberand to each of said movable contacts for simultaneously moving saidcontacts between open and closed positions, an operating member movablefrom a first position to a second position to latch each of saidlatching members in its associated holding member, movement of saidoperating members from said second position to its first positionplacing said overcenter means in a rigid condition to close said movablecontacts, common trip means coupled to said second holding member and toeach of said overcurrent responsive means so that the occurrence 1of anoverload current through any of said poles will pivot said secondholding member to release said second latching member for rotation bysaid biasing means to rotate said first holding member out of latchingengagement with said first latching member whereby said overcenter meansis released for simultaneous opening of said movable contacts.

8. A circuit breaker comprising main fixed and main movable contactmeans and overcurrent responsive means in circuit with said main contactmeans, a collapsible linkage assembly coupled to said main movablecontact means, a latching assembly for holding said collapsible linkagemeans in `a rigid condition so that said main movable contact means isclosed, an operating member movable in a first direction t-o place saidlatching assembly in a latched condition, subsequent movement of saidoperating member in an opposite direction placing said linkage assemblyin a rigid condition to close said main movable contact means,overcurrent responsive means, trip means coupled to said latchingassembly and to said overcurrent responsive means, said over-currentresponsive means -operable upon th-e occurrence of an overcurrent tooperate said trip means for releasing said latching assembly so thatsaid main contact means is opened, a signal light assembly including asignal light and a rotatable auxiliary contact member and a fixedc-ontact member, said auxiliary contact member having a lat-ch portionand a pair of contact portions engageabl-e with said fixed contactmember upon rotation in either direction, spring means resilientlyurging one of said contact portions into engagement with saidstation-ary contact, said latch portion being engageable with saidlatching assembly to normally prevent rotation of said auxiliary contactmember, operation of said overcurrent responsive means 'being -operableto unlatch said auxiliary contact member for rotation of said onecontact portion into er1- References Cited bythe Examiner UNITED STATESPATENTS Dorfman 200-116 S-andin 200-116 Runke 20G-116 Bennett 200-109Case 20D-116 Cellerini et al 20G-88 Walker et al 200-88 Steven et al.20G-88 BERNARD A. GILHEANY, Primary Examiner.

6. A THREE-POLE CIRCUIT BREAKER, EACH POLE INCLUDING OVERCURRENTRESPONSIVE MEANS AND FIXED AND MOVABLE CONTACT MEANS, A SINGLE LATCHINGASSEMBLY COMMON TO ALL OF SAID POLES, SAID LATCHING ASSEMBLY INCLUDINGFIRST AND SECOND INDEPENDENT PIVOTAL LATCHING MEMBERS, FIRST AND SECONGINDEPENDENTLY PIVOTAL HOLDING MEMBERS FOR RESPECTIVELY MAINTAINING SAIDFIRST AND SECOND LATCHING MEMBERS IN A LATCHED POSITION, BIASING MEANSRESILIENTLY URGING SAID SECOND LATCHING MEMBER INTO RESILIENT ENGAGEMENTWITH SAID FIRST HOLDING MEMBER FOR RESILIENTLY URGING SAID FIRST HOLDINGMEMBER TOWARD PIVOTAL MOVEMENT IN A LATCH RELEASING DIRECTION WHEN SAIDSECOND LATCH MEMBER IS RELEASED FROM ITS LATCHED POSITION AND ALLOWINGSAID FIRST HOLDING MEMBER TO RETURN TO ITS HOLDING POSITION WHEN SAIDSECOND LATCHING MEMBER IS IN ITS LATCHED POSITION, AN OVERCENTERASSEMBLY COUPLED TO SAID FIRST LATCHING MEMBER AND TO EACH OF SAIDMOVABLE CONTACTS FOR SIMULTANEOUSLY MOVING SAID CONTACTS BETWEEN OPENAND CLOSED POSITIONS, AN OPERATING MEMBER MOVABLE FROM A FIRST POSITONTO A SECOND POSITION TO LATCH EACH OF SAID LATCHING MEMBERS ON ITSASSOCIATED HOLDING MEMBER, MOVEMENT OF SAID OPERATING MEMBER FROM SAIDSECOND POSITION TO ITS FIRST POSITION PLACING SAID OVERCENTER MEANS IN ARIGID CONDITION TO CLOSE SAID MOVABLE CONTACTS, COMMON TRIP MEANSCOUPLED TO SAID SECOND HOLDING MEMBER AND TO EACH OF SAID OVERCURRENTRESPONSIVE MEANS SO THAT THE OCCURRENCE OF AN OVERLOAD CURRENT THROUGHANY OF SAID POLES WILL PIVOT SAID SECOND HOLDING MEMBER TO RELEASE SAIDSECOND LATCHING MEMBER FOR ROTATION BY SAID BIASING MEANS TO ROTATE SAIDFIRST HOLDING MEMBER OUT OF LATCHING ENGAGEMENT WITH SAID FIRST LATCHINGMEMBER WHEREBY SAID OVERCENTER MEANS IS RELEASED FOR SIMULTANEOUSOPENING OF SAID MOVABLE CONTACTS.